#include "HMACSHA256.h"

// 根据传入的明文和密钥，返回一个由 HMACSHA256 算法加密后的密文
static uint32_t ror(uint32_t n, uint32_t k)
{
  return (n >> k) | (n << (32 - k));
}

#define ROR(n, k) ror(n, k)

#define CH(x, y, z) (z ^ (x & (y ^ z)))
#define MAJ(x, y, z) ((x & y) | (z & (x | y)))
#define S0(x) (ROR(x, 2) ^ ROR(x, 13) ^ ROR(x, 22))
#define S1(x) (ROR(x, 6) ^ ROR(x, 11) ^ ROR(x, 25))
#define R0(x) (ROR(x, 7) ^ ROR(x, 18) ^ (x >> 3))
#define R1(x) (ROR(x, 17) ^ ROR(x, 19) ^ (x >> 10))

static const uint32_t K[64] =
    {
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2};

static void sha256_transform(SHA256_CTX *s, const uint8_t *buf)
{
  uint32_t t1, t2, a, b, c, d, e, f, g, h, m[64];
  uint32_t i, j;

  for (i = 0, j = 0; i < 16; i++, j += 4)
  {
    m[i] = (uint32_t)buf[j] << 24 | (uint32_t)buf[j + 1] << 16 |
           (uint32_t)buf[j + 2] << 8 | (uint32_t)buf[j + 3];
  }
  for (; i < 64; i++)
  {
    m[i] = R1(m[i - 2]) + m[i - 7] + R0(m[i - 15]) + m[i - 16];
  }
  a = s->h[0];
  b = s->h[1];
  c = s->h[2];
  d = s->h[3];
  e = s->h[4];
  f = s->h[5];
  g = s->h[6];
  h = s->h[7];
  for (i = 0; i < 64; i++)
  {
    t1 = h + S1(e) + CH(e, f, g) + K[i] + m[i];
    t2 = S0(a) + MAJ(a, b, c);
    h = g;
    g = f;
    f = e;
    e = d + t1;
    d = c;
    c = b;
    b = a;
    a = t1 + t2;
  }
  s->h[0] += a;
  s->h[1] += b;
  s->h[2] += c;
  s->h[3] += d;
  s->h[4] += e;
  s->h[5] += f;
  s->h[6] += g;
  s->h[7] += h;
}

void sha256_init(SHA256_CTX *s)
{
  s->len = 0;

  s->h[0] = 0x6a09e667;
  s->h[1] = 0xbb67ae85;
  s->h[2] = 0x3c6ef372;
  s->h[3] = 0xa54ff53a;
  s->h[4] = 0x510e527f;
  s->h[5] = 0x9b05688c;
  s->h[6] = 0x1f83d9ab;
  s->h[7] = 0x5be0cd19;
}

void sha256_final(SHA256_CTX *s, uint8_t *md)
{
  uint32_t r = s->len % SHA256_BLOCKLEN;
  int i;

  // pad
  s->buf[r++] = 0x80;
  if (r > 56)
  {
    memset(s->buf + r, 0, SHA256_BLOCKLEN - r);
    r = 0;
    sha256_transform(s, s->buf);
  }
  memset(s->buf + r, 0, 56 - r);
  s->len *= 8;
  s->buf[56] = s->len >> 56;
  s->buf[57] = s->len >> 48;
  s->buf[58] = s->len >> 40;
  s->buf[59] = s->len >> 32;
  s->buf[60] = s->len >> 24;
  s->buf[61] = s->len >> 16;
  s->buf[62] = s->len >> 8;
  s->buf[63] = s->len;
  sha256_transform(s, s->buf);

  for (i = 0; i < SHA256_DIGESTINT; i++)
  {
    md[4 * i] = s->h[i] >> 24;
    md[4 * i + 1] = s->h[i] >> 16;
    md[4 * i + 2] = s->h[i] >> 8;
    md[4 * i + 3] = s->h[i];
  }
  sha256_init(s);
}

void sha256_update(SHA256_CTX *s, const uint8_t *m, uint32_t len)
{
  const uint8_t *p = m;
  uint32_t r = s->len % SHA256_BLOCKLEN;

  s->len += len;
  if (r)
  {
    if (len + r < SHA256_BLOCKLEN)
    {
      memcpy(s->buf + r, p, len);
      return;
    }
    memcpy(s->buf + r, p, SHA256_BLOCKLEN - r);
    len -= SHA256_BLOCKLEN - r;
    p += SHA256_BLOCKLEN - r;
    sha256_transform(s, s->buf);
  }
  for (; len >= SHA256_BLOCKLEN; len -= SHA256_BLOCKLEN, p += SHA256_BLOCKLEN)
  {
    sha256_transform(s, p);
  }
  memcpy(s->buf, p, len);
}

#define INNER_PAD '\x36'
#define OUTER_PAD '\x5c'

void hmac_sha256_init(HMAC_SHA256_CTX *hmac, const uint8_t *key, uint32_t keylen)
{
  SHA256_CTX *sha = &hmac->sha;
  uint32_t i;

  if (keylen <= SHA256_BLOCKLEN)
  {
    memcpy(hmac->buf, key, keylen);
    memset(hmac->buf + keylen, '\0', SHA256_BLOCKLEN - keylen);
  }
  else
  {
    sha256_init(sha);
    sha256_update(sha, key, keylen);
    sha256_final(sha, hmac->buf);
    memset(hmac->buf + SHA256_DIGESTLEN, '\0', SHA256_BLOCKLEN - SHA256_DIGESTLEN);
  }

  for (i = 0; i < SHA256_BLOCKLEN; i++)
  {
    hmac->buf[i] = hmac->buf[i] ^ OUTER_PAD;
  }

  sha256_init(sha);
  sha256_update(sha, hmac->buf, SHA256_BLOCKLEN);
  // copy outer state
  memcpy(hmac->h_outer, sha->h, SHA256_DIGESTLEN);

  for (i = 0; i < SHA256_BLOCKLEN; i++)
  {
    hmac->buf[i] = (hmac->buf[i] ^ OUTER_PAD) ^ INNER_PAD;
  }

  sha256_init(sha);
  sha256_update(sha, hmac->buf, SHA256_BLOCKLEN);
  // copy inner state
  memcpy(hmac->h_inner, sha->h, SHA256_DIGESTLEN);
}

void hmac_sha256_update(HMAC_SHA256_CTX *hmac, const uint8_t *m, uint32_t mlen)
{
  sha256_update(&hmac->sha, m, mlen);
}

void hmac_sha256_final(HMAC_SHA256_CTX *hmac, uint8_t *md)
{
  SHA256_CTX *sha = &hmac->sha;
  sha256_final(sha, md);

  // reset sha to outer state
  memcpy(sha->h, hmac->h_outer, SHA256_DIGESTLEN);
  sha->len = SHA256_BLOCKLEN;

  sha256_update(sha, md, SHA256_DIGESTLEN);
  sha256_final(sha, md); // md = D(outer || D(inner || msg))

  // reset sha to inner state -> reset hmac
  memcpy(sha->h, hmac->h_inner, SHA256_DIGESTLEN);
  sha->len = SHA256_BLOCKLEN;
}

void pbkdf2_sha256(HMAC_SHA256_CTX *hmac,
                   const uint8_t *key, uint32_t keylen, const uint8_t *salt, uint32_t saltlen, uint32_t rounds,
                   uint8_t *dk, uint32_t dklen)
{
  uint8_t *U;
  uint8_t *T;
  uint8_t count[4];
  uint32_t i, j, k;
  uint32_t len;

  uint32_t hlen = SHA256_DIGESTLEN;
  uint32_t l = dklen / hlen + ((dklen % hlen) ? 1 : 0);
  uint32_t r = dklen - (l - 1) * hlen;

  hmac_sha256_init(hmac, key, keylen);

  U = hmac->buf;
  T = dk;

  len = hlen;
  for (i = 1; i <= l; i++)
  {
    if (i == l)
    {
      len = r;
    }
    count[0] = (i >> 24) & 0xFF;
    count[1] = (i >> 16) & 0xFF;
    count[2] = (i >> 8) & 0xFF;
    count[3] = (i) & 0xFF;
    hmac_sha256_update(hmac, salt, saltlen);
    hmac_sha256_update(hmac, count, 4);
    hmac_sha256_final(hmac, U);
    memcpy(T, U, len);
    for (j = 1; j < rounds; j++)
    {
      hmac_sha256_update(hmac, U, hlen);
      hmac_sha256_final(hmac, U);
      for (k = 0; k < len; k++)
      {
        T[k] ^= U[k];
      }
    }
    T += len;
  }
}


/**
 * @brief 加密算法外露 API
 *
 * @param output  存放加密后的密文的字符串空间，需提前准备好
 * @param input   待加密的明文（末端以\0结尾）
 * @param key     密钥（末端以\0结尾）
 */
void HMACSHA256_encrypt(char *output, uint8_t *input, uint8_t *key){
  HMAC_SHA256_CTX hmac;
  uint8_t temp[32]; // 临时存储加密后的密文
	hmac_sha256_init(&hmac, key, strlen((char *)key));
	hmac_sha256_update(&hmac, input, strlen((char *)input));
	hmac_sha256_final(&hmac, temp);
  uint8_t i = 0;
  for(; i < SHA256_DIGESTLEN; i++){
    if(temp[i]/16 < 10)
      output[2*i] = temp[i]/16+'0';
    else
      output[2*i] = temp[i]/16-10+'a';

    if(temp[i]%16 < 10)
      output[2*i+1] = temp[i]%16+'0';
    else
      output[2*i+1] = temp[i]%16-10+'a';

  }
  output[2*i] = 0;
}
